Bartel BM-5
The Bartel BM-5 was a Polish biplane advanced trainer used from 1930 to 1939 by the Polish Air Force, manufactured in the Samolot factory in Poznań. Design and development The aircraft was designed by Ryszard Bartel in Samolot factory in Poznań, as an advanced trainer, transitory between primary trainers and bomber or reconnaissance aircraft. Bartel had worked since 1926 on his BM-3 advanced trainer design, the preliminary design for which won a military contest, but in the meantime he developed a quite successful primary trainer Bartel BM-4 and then decided to model the advanced trainer upon that plane, to obtain better durability. The result was the BM-5 design. The BM-5 prototype was built in 1928 and flown on 27 July that year in Poznań. It had good handling, high stability and spin resistance, which made it a suitable trainer for larger aircraft. A distinguishing feature of all Bartels was an upper wing of a shorter span, because lower and upper wing halves were interchangeable (i.e. the lower wingspan included the width of the fuselage). The first prototype was designated BM-5a and was fitted with a Austro-Daimler inline engine. The second prototype, flown on 15 April 1929, was designated BM-5b and was fitted with a SPA-6A inline engine, then was refitted in August with a Hispano-Suiza 8Fb V-engine and redesignated BM-5c (it was meant to utilize engine stores from the Bristol F.2 Fighter). Next 20 aircraft of each type were built: BM-5a, BM-5b and BM-5c. A disadvantage of most BM-5s were old and faulty engines. From all the variants the BM-5a variant was the heaviest and had the worst performance. For that reason in 1935 one BM-5 was fitted at the PZL works with a Wright Whirlwind J-5 radial engine, produced in Poland (in Polish Skoda Works, then Avia). This variant was designated the BM-5d and 20 of BM-5a and BM-5b were next converted to BM-5d. Operational history BM-5s were used in the Polish Air Force for training from 1930, in a central pilots' school in Dęblin. 5 BM-5c's were used in Naval Air Unit (MDLot) in Puck. Most were written off in the second half of 1930s and replaced with the PWS-26. Some survived until the German invasion of Poland in September 1939. None survived the war. Operators ; *Polish Air Force Specifications (BM-5d) Description Wooden construction biplane. Fuselage rectangular in cross-section, plywood covered (engine section - aluminum covered). Rectangular two-spar wings, plywood and canvas covered. Crew of two, sitting in tandem in open cockpits, with individual windshields and twin controls, instructor in rear cockpit. Fixed landing gear, with a rear skid. Engine in front, with a water radiator below fuselage nose (BM-4a,b,c). Two-blade wooden propeller. Fuel tanks in upper wings and fuselage, capacity: 235-270 l. Engines used: *BM-5a: Austro-Daimler 6-cylinder straight engine, water-cooled, nominal power *BM-5b: SPA-6A 6-cylinder straight engine, water-cooled, take-off power, nominal power *BM-5c: Hispano-Suiza 8Fb 8-cylinder V-engine, water-cooled, take-off power, nominal power *BM-5d: Wright Whirlwind J-5 9-cylinder radial engine, take-off power, nominal power References *Andrzej Glass: "Polskie konstrukcje lotnicze 1893-1939" (Polish aviation constructions 1893-1939), WKiŁ, Warsaw 1977 (Polish language, no ISBN) External links *Photos and drawings at Ugolok Neba site (in Russian) BM-5 Category:Biplanes Category:Single-engined tractor aircraft Category:1920s Polish military trainer aircraft